Manufacture of hard sintered alloys



Patented May 9, 1950 lJNlTE- rte- 218 File "MANUFACTURED F HARD SINTERED ALLOYS "Marcel Oswald, PariQTr-ance, assignorptowsociete Le Carbone-Iaorraine-yParis, France "No Drawing. Application 1'! uly -30; 1947 ,Serial No. 7643899; In France July 4, 1941- *SectionL'PublifcLaw sea-'Augus'esaisic Patent expires July 4 1961 .6 Claims.

1 This invention relates tosintered hard alloys including zirconium carbide arid other refractory carbides-,such as the'tungsten, titanium, vanadium, tantalum, "etc.,' carbides. The 'agglomera- 7 tion is in all cases obtained'by'means of a more fusible auxiliary-metal or alloy. To all these a1- loys, zirconium carbide gives advantagesdue to its extreme hardness and 'to a greatly reduced coefficient of friction when cutting steels.

It has not been possible to introduce intoindustry the hard'sintered alloys of "zirconium carbide already known, because-they'havenumerous blow-holes, especially-when they'are rich in -z'ir-- conium carbide.

The processforming the subject matter ofthe invention does away withthis 'disadvantage'by making use of a new double 'zirconiu'm and tungsten carbide representdby'the formula Z'13WC4 orof solid solutions of'said carbide and'the double.

titanium and tungsten carbide'ThWCa The zirconium and tungsten doubleicarbide is produced by mixingsto'ichiometrically calculated; proportions of reduciblelcompoundsiiof. zirconium; and tungsten, as, for instance, the: oxides ZrQ'i and W0: with the quantity 50f carbon: necessary for reduction and carburisation. -These.:-sub1- stances in a fine'powdera'revery carefully. mixed: and-- then heated in a vacuum: furnace; so as 1J0 reach a temperature-of at-least 2000 C. The

gases given off are pumped away as and when formed. A solidsolution-havingthe composition 3ZrC.WC is thus produced, the atomiadistribu tion of which is rearranged to convert the solid;

solution into the double carbide correspondingto the formula Zr'BWCibya suitablethermal treat?- me'nt, namely slow cooling froml600 C. to 1000 C. approximately. The double carbide'has'beenalways.very-fragile and-porous. The double carbide .on. the contrary is well-wetted by metals and alloysofzthe iron group andgives satisfactory si-ntered alloys. I V

, The results are still better. if the double carbide ZI'BWC- is replaced a solid solution of this carbide with..the double tungsten andstitani-um carbide. In thesesolutionsthe atoms oititanium and 'zirconium take one anothersplaces-atz random in the crystalline system in which they occupy the:"centresofthe faces'ottheunit cells, the corners of said cells. being: left: for the tungsten atoms. Solidsolutions of simple carbides are 'already'lm'own, 'as',ffor'infstance,.titanium carhide and molybdenum, 'ortungste'n carbide, but

not those betweenuouble carb'ideswhich are now. In order-to preparesolid solutions of the type (Ti, ZilsV/Cij reducible'compounids' oi the three metals titanium, "zirconium and tungsten are mixed incalculatedmroporti'ons, so'that' for each" atom of tungsten, this mixture contains three atoms of titaniumand-ziroonium together. The required quantity of carbon is also incorporated to enable-reduction"and carburisation to be effected. These operationsare carriedout between about: 2000 C: and 2300" j 0;, according to p the same process as forthe double carbide ZraWCi. In order to produce therequired-structure, cooling may take place at a.suitable speedfrom about 1.600? C..to.l-000." C torinstance, in from lOto 30 hours and-atrany speed atlother temperatures.

} Solid solutions :in-;particular. have been preparedin which theaatomic proportion of'tita-nium and zirconiumhasohe oftheyalues 1:2, 1:1, 2:1,-

prepared by redu'ctionan'd carburisation at 2200" Gil-2300* C. by'maintaining the temperature above 2100 C. for about two hours, allowing-to cool in' Increase. in the proportion oftitanium slightly reduces the hardness of. the solid-solution and increases.therfrictional--.coeificient of the sintered alloys,.but toransadmissible degree so longv as the atomic ratio T ii Zr :does not exceed the value of 2.5 approx'irnately...

By using a solid solution, briefly described as triple carbide containing two atoms of titanium per-atom offzlrconiumaaccording. to the formula TiiiZrW'Gl, hezqualityiof-tlie alioyswitlrzirconium carbide is in the end improved, because theipreparation is considerably facilitated, especially in the" reduction andcarbu'risation phase. 7

Inor'der' tofpreparesintered alloys forming the subject" matter of the" invention, the zirconiumcar bicle'or the"doublecarbide ZraWCl, or a' solids'olutio'n" of thetype (Zifli) 3WC4, is mixed with thefothercomponents: hard carbides, auxiliaiiyimfetalslor alloys; according to theknown' technical methods; "Ea'chlof'tlie' constituents is iii the formbfa fine powder. Afterhomogenisation, compression and sintering are carried out at a high temperature according to the usual methods. I shall now describe a few examples:

Example 1.Zirconium carbide, tungsten carbide and cobalt The compositions of this type are to be recommended, especially for proportions of carbide ZrC below about 20% by weight.

Example Double carbide of zirconium and tungsten 13 Tungsten carbide 81 Cobalt It is preferable to prepare the mixture of tungsten carbide and cobalt by liberating the auxiliary metal and the refractory metal simultaneously in the nascent state by the action of a reducing and carburising gas such as coal gas so that there is simultaneously produced a condensation of pulverulent material which distributes itself in contact with the metallic grains and prevents them from growing; and then to incorporate the double carbide, make the mixture homogeneous, and press and sinter according to the known methods. Firing may take place in'vacuo and at a temperature of 1600 C. to 1650 C. The alloys so obtained are slightly fragile but very hard.

Example 2.Zirconium carbide, titanium carbide, tungsten carbide, and a binding agent Triple carbide TizZI W04 12 32 Tungsten carbide 82 61. 5 Cobain 6 5. 5 Ir 1 v The usual processes may be used, but there is advantage in preparing separately mixtures of tungsten carbide and binding metals in accordance with the process referred to in connection with Example 1 above: for (a) the whole of the tungsten carbide and cobalt: for (b) the tungsten carbide with 3.5 parts of cobalt and the whole quantity of iron. The compositions thus prepared are mixed with the triple carbide, and for (b) with the complement of cobalt, and then they are compressed and fired in an inert gas, in hydrogen or in vacuo between 1550 C. and 1600 C.

Example 3.Zirconzum carbide titanium carbide-tungsten carbidetantalum carbide and binder The alloys prepared according to the preceding examples become more tenacious if they contain a percentage below about 8% of one or more carbides of metals belonging to the fifth periodic group; vanadium, columbium or tantalum. The three following compositions are respectively derived from those given in Examples 1 and 2, with additions of tantalum carbide and columbium carbide. The alloy (C) is preferably prepared 4 from the double carbide Zr3WC4 and the alloys (D), (E) from the triple carbide Ti2ZrWC4.

Example 4.-Inflaence of vanadium and chromium The vanadium incorporated in the alloys of the foregoing types, diminishes or avoids blowholes and prevents enlargement of the grains. Harder and more tenacious alloys are then obtained, especially if a very small percentage of chromium is also added. The whole percentage of vanadium and chromium must be limited to less than 5% of the total weight and more often below 2%. The incorporation of vanadium and eventually of chromium, is carried out as described in the specification of my co-pending application Serial No. 764,901, filed July 30, 1947, now abandoned. It is possible to modify in this way the alloys above-mentioned, as examples, by the addition of vanadium and optionally of chromium, namely 1% of vanadium and 0.5% of chromium. Starting from the composition (B) of Example 2, the following alloy has been obtained and gives the best results:

Triple carbide Ti2ZrWC4 32 Tungsten carbide 60 Vanadium 1 Chromium 0.5

Cobalt 5.5

Iron u--. 1

The preparation of the powder to be sintered comprises, on the one hand, the manufacture of the triple carbide, and, on the other hand, the preparation of the mixture of the other constituents according to the aforementioned patent application, the mixture of the whole in the requisite proportions, pressing and firing. It is also possible to reduce the quantities of cobalt and/or iron introduced in the mixture of constituents other than the triple carbide, and to incorporate directly the remainder of the cobalt and/or of the iron in the final mixture as described in Example 2.

In cutting operations, especially at high speeds, the alloys of zirconium carbide reduce the frictional coefficient and render the operation almost noiseless, which is a new and unforeseen result. The noise in workshops is injurious to the auditive organs and to the nervous system; alloys with zirconium carbide, therefore, constitute desirable improvement.

In the above description it has been assumed that the zirconium carbide was prepared from an initial material free from hafnium. Now, most zirconium ores contain hafnium. Experience has shown that it is useless to separate these two elements; the small quantities of hafnium carbide eventually present exercise noharmful influence on the quality of the alloys. When there is hafnium present, the double carbide ZI3WC4 is actually a solid solution (Zr, Hf )3WC4 in which is incorporated with this solid solution, a solid solution of the type (Zr.Ti.Hf)3WC4 is therefore obtained. In the whole description and in the claims the word zirconium designates either that metal or the natural and difificultly separable mixtures of zirconium and hafnium.

I claim:

1. Process of manufacturing sintered hard alloys, which comprises reducing and carburizing a finely powdered mixture of reducible compounds of zirconium and tungsten in the stoichiometric proportions of 3Zr to 1W, with carbon sufiicient for reduction of said compounds to the metallic state and for carburization of the liberated metals, at a temperature between about 2000 C. and about 2300 C. while pumpin off simultaneously liberated reaction gases, whereby to form a solid solution having the composition 3ZrC.WC, cooling the solid solution at a controlled slow rate through the temperature range from 1600 C. down to 1000 C. so as to rearrange the metallic atoms in the common crystalline lattice according to a superlattice, whereby to convert the solid solution into a cubic double carbide compound corresponding to the formula Zr3WC4, forming a homogeneous finely powdered mixture of an appreciable amount of said double carbide, at least one metal of the iron group, and at least one refractory metal carbide selected from the group consisting of tungsten carbide, titanium carbide, vanadium carbide, tantalum carbide, molybdenum carbide, chromium carbide and columbium carbide, compressing the mixture and sintering at a temperature between about 1200 C. and about 1600 C.

2. Process of manufacturing sintered hard alloys, which comprises reducing and carburizing a finely powdered mixture of reducible compounds of zirconium, titanium and tungsten in the proportions of 3 (TiZr together) to 1W, with carbon sufiicient for reduction of said compounds to the metallic state and for carburization of the liberated metals, at a temperature between about 2000 C. and about 2300 0., whereby to form a solid solution of zirconium, titanium and tungsten carbides, cooling the solid solution at a controlled slow rate through the temperature range from 1600 C. down to l000 C. so as to rearrange the atoms of tungsten at the corners of the elementary cubes in the mixed lattice and form a solid solution of double carbides corresponding to the formulae ZrsWCl and TisVJCe in which the atoms of tungsten occupy the corners and the atoms of zirconium and of titanium are distributed at random at the centres of the races of the elementary cubes, forming a homogeneous finely powdered mixture of an appreciable amount of the cooled solid solution, at least one metal of the iron group, and at least one refractory metal carbide selected from the group consisting of tungsten carbide, vanadium carbide, tantalum carbide, molybdenum carbide, chromium carbide and columbium carbide, compressing the mixture and sintering at a temperature between about 1200 C. and about 1600 C.

3. Process as defined in claim 2, wherein the atomic ratio of titanium/ zirconium is between 1 :2 and about 2.511.

4. Process of manufacturing a sintered hard carbide composition of zirconium and tungsten, which comprises forming an intimate finely powdered mixture of oxides of zirconium and tungsten in the stoichiometric proportions of 3Z1O2 to 1WO3 with an amount of carbon suflicient for reduction of said oxides to the metallic state and for carburization of the liberated metals, heating said mixture to a temperature of between about 2000 C. and about 2300 C. in vacuo while pumping off simultaneously liberated reaction gases, whereby to reduce said oxides and carburize the liberated metals, with the elimination of oxygen from the reaction mass, to form a solid solution of tungsten carbide in zirconium carbide having the composition SZrCWC, cooling said solid solution to 1600 C. in a period of one hour, then from 1600 C. to 1200 C. in a period of from eight to twenty-four hours, and then from 1200 C. to 1000 C. in from two to four hours so as to rearrange the metallic atoms in the common crystalline lattice to form a superlattice, whereby to convert said solid solution into a cubic double carbide compound corresponding to the formula Zr3WC4, forming a homogeneous finely powdered mixture of an appreciable amount of such double carbide, cobalt and tungsten carbide, compressing the lastmentioned mixture and sintering at a temperature between about 1200 C. and about 1600" C.

5. Process as defined in claim l, wherein the amount of said double carbide incorporated in said mixture last-mentioned is such as to provide in the sintered composition a zirconium content calculated as ZrC, of less than about 10% by weight.

6. Process of manufacturing a sintered hard carbide composition of zirconium, titanium and tungsten, which comprises forming an intimate finely powdered mixture of reducible compounds of zirconium, titanium and tungsten in proportions such that said mixture contains two atoms of titanium and one atom of zirconium for each atom of tungsten and with carbon sufficient for reduction of said compounds to the metallic state and for carburization of the liberated metals, heating said mixture to a temperature of between about 2000 C. and about 2300 C. in vacuo while pumping off simultaneously liberated reaction gases, whereby to reduce said compounds and carburize the liberated metals with the elimination of oxygen from the reaction mass, to form a solid solution of zirconium, titanium and tungsten carbides, cooling said solid solution through the temperature range from 1600 C. down to 1000 C. in from ten to thirty hours so as to rearrange the atoms of tungsten at the corners of the elementary cubes in the mixed lattice and form a solid solution of double carbides corresponding to the formulae ZI3WC4 and Ti3WC4 in which the atoms of tungsten occupy the corners and the atoms of zirconium and of titanium are distributed at random at the centres of the faces of the elementary cubes, forming a finely homogeneous mixture of cobalt, tungsten carbide and an amount of said solid solution of double carbides such as to provide in the final product a zirconium content, calculated as ZrC, of less than about 10% by Weight, compressing the last-mentioned mixture and sintering at a temperature between about 1200 C. and about 1600 C.

MARCEL OSWALD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,122,157 Schwarzkopf June 28, 1938 2,137,144 Sainderichin Nov. 15, 1938 2,170,432 Schwarzkopf Aug. 22, 1939 2,188,983 Padowicz Feb. 6, 1940 2,253,969 Dawihl et al. Aug. 26, 1941 Certificate of Correction Patent No. 2,507,218 May 9, 1950 MAROEL OSWALD It is hereby certified that error appears in the printed specification of the above 7 numbered patent requirmg correction as follows:

Column 3, line 9, for 20% read 10%; column 4, line 8, in the table, fourth column thereof, for 72.35 read 73.25;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 14th day of November, A. D. 1950.

THOMAS F. MURPHY,

Assistant C'ommz'asz'oner of Patents.

Certificate of Correction Patent No. 2,507,218 May 9, 1950 MAROEL OSWALD It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 9, for 20% read 10%; column 4, line 8, in the table, fourth column thereof, for 72.35 read 73.25;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 14th day of November, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents. 

1. A MIX FOR MAKE REFRACTORY CONCRETE CONSISTING OF FROM 5 TO 60% OF CALCIUM-ALUMINATE CEMENT AND FROM 40 TO 95% CALCINED CLAY CONTAINING FROM 50 TO 99% ALUMINA, ONE OF SAID COMPONENTS CONTAINING FROM 1 TO 25% HYDROGEN FLUORIDE. LOYS, WHICH COMPRISES REDUCING AND CARBURIZING A FINELY POWDERED MIXTURE OF REDUCIBLE COMPOUNDS OF ZIRCONIUM AND TUNGSTEN IN THE STOICHIOMETRIC PROPORTIONS OF 3ZR TO 1W, WITH CARBON SUFFICIENT FOR REDUCTION OF SAID COMPOUNDS TO THE METALLIC STATE AND FOR CARBURIZATION OF THE LIBERATED METALS, AT A TEMPERATURE BETWEEN ABOUT 2000*C. AND ABOUT 2300*C. WHILE PUMPING OFF SIMULTANEOUSLY LIBERATED REACTION GASES, WHEREBY TO FORM A SOLID SOLUTION HAVING THE COMPOSITION 3ZRC.WC, COOLING THE SOLID SOLUTION AT A CONTROLLED SLOW RATE THROUGH THE TEMPERATURE RANGE FROM 1600*C. DOWN TO 1000*C. SO AS TO REARRANGE THE METALLIC ATOMS IN THE COMMON CRYSTALLINE LATTICE ACCORDING TO A SUPERLATTICE, WHEREBY TO CONVERT THE SOLID SOLUTION INTO A CUBIC DOUBLE CARBIDE COMPOUND CORRESPONDING TO THE FORMULA ZR3WC4, FORMING A HOMOGENEOUS FINELY POWDERED MIXTURE OF AN APPRECIABLE AMOUNT OF SAID DOUBLE CARBIDE,, AT LEAST ONE METAL OF THE IRON GROUP, AND AT LEAST ONE REFRACTORY METAL CARBIDE SELECTED FROM THE GROUP CONSISTING OF TUNGSTEN CARBIDE, TITANIUM CCARBIDE, VANADIUM CARBIDE, TANTALUM CARBIDE, MOLYBDENUM CARBIDE, CHROMIUM CARBIDE AND COLUMBIUM CARBIDE, COMPRESSING THE MIXTURE AND SINTERING AT A TEMPERATURE BETWEEN ABOUT 1200*C. AND ABOUT 1600*C. 